of the Fishery Board for Scotland. 



337 



colour was too frequently mixed with different forms of growth to allow 

 of the supposition it was a secondary result of the growth of such organ- 

 ism as Mucor, &c, with which it occurred. Although occurring so fre- 

 quently we had at first great difficulty in isolating the organism. 



When separated in a tolerably pure condition it was at first thought to be 

 the Micrococcus prodigiosus. But further study, especially after thorough 

 purification, shewed that it presents striking differences from that organ- 

 ism, and we have therefore called it provisionally the Magenta micrococcus, 

 since in colour and iridescence it so strikingly resembles magenta. Its 

 points of difference from the Micrococcus prodigiosus will be more fully 

 stated later. The water from which it was actually isolated was taken 

 from the Tweed near Melrose. 



Plate Cultivation. — Growth becomes visible to naked eye on third day, 

 in the form of small greyish points, some of which have already a faint 

 pinkish tinge. On the fourth day, the colour has assumed a bright red 

 or magenta in many of the points, the largest of which are now about the 

 size of a small pin's-head. The individual points of growth slowly enlarge, 

 but do not usually exceed a pin's-head in size, and very speedily those 

 which were grey in colour become of the prevailing magenta hue. The 

 brilliant magenta colour is first seen in those growths nearest the surface 

 of the gelatine, those implanted deeper only acquiring it when they reach 

 the surface. Very soon each magenta point presents a peculiar iridescent 

 appearance by reflected light — similar to the appearance seen when 

 magenta is dropped on to the surface of glass. This iridescence by 

 reflected light also characterises the growth on bread paste and potato. 

 Under a low magnifying lens — about 20 diameters — the points of growth 

 are seen to consist of globular bodies, with well-defined, or in some cases 

 slightly irregular margins, and dark reddish or brown granular-looking 

 contents. The growths do not cause liquefaction of gelatine on plate. 



Microscopically. — Organisms mounted on the fourth day from gelatine 

 plate, and stained, were found to consist of micrococci from *4 to "75 /x — 

 mostly about "6 /x. These occurred singly, or in pairs or heaps, or 

 chains. In a few cases groups of four were seen. The micrococci are 

 slightly ovoid, but the average longer diameter is about *6 fx. 



Test Tubes. — A faint pinkish spot is seen at point of inoculation of 

 gelatine on the first day, and a delicate greyish streak along the needle- 

 track. On the second day after inoculation the growth on the surface of 

 the gelatine has increased considerably in size, and is of a bright red or 

 magenta colour. The bright red surface growth rapidly increases, and 

 soon spreads over almost the whole of the surface of the gelatine. Along 

 the needle-track the extension of growth is very slow, being in the form 

 of delicate scolloped processes, which gradually pass into surrounding 

 gelatine. The colour of the growth along needle-track remains grey in 

 appearance. After the lapse of several weeks, liquefaction takes place 

 immediately beneath the surface growth around the upper part of the 

 needle track, and extends downwards, so that in certain cases a film of 

 the magenta growth may be seen floating on the surface of the liquid 

 gelatine, which may be comparatively clear or somewhat opalescent ; and 

 at the bottom a greyish sediment may be observed. In other tubes, 

 especially if the gelatine is rather less firm, liquefaction takes place more 

 rapidly, and the liquid jelly has a uniform red tinge, with a copious red 

 sediment at bottom. This appearance may also be observed when a larger 

 quantity of material is inoculated into jelly of ordinary strength, in which 

 case liquefaction takes place around needle-track before the surface 

 growth has had time to make much progress, and so we get a very delicate 

 flocculent film of a pinkish hue on surface, and a reddening of the liquid 



